The present invention relates in general to semiconductor wafer processing and, more particularly, to trapping particulate by-products from a chemical vapor deposition process during manufacture of semiconductor wafers.
It is well known in the art that semiconductor wafer processing for integrated circuits includes processes that require chemical vapor depositions such as nitride, polysilicon, and low temperature oxide depositions. Semiconductor wafers are placed in a quartz crystal tube that is housed in a high temperature reactor. The reactor is typically a low pressure chemical vapor deposition (LPCVD) reactor. A continuous flow gaseous vapor that has been heated to a high temperature is drawn through the LPCVD reactor to cause the desired chemical reaction to take place with the semiconductor wafers. The vapor exits the reactor chamber through a pipe that connects to a trap filter. A vacuum pump draws the vapor from the reactor chamber through the trap filter to capture particulate by-products from the heated vapor. The remaining vapor is passed on to a scrubber to further neutralize the toxic effects of the exhausted gas.
The vapor particulates produced by the LPCVD process have a tendency to accumulate in the pipe at the inlet of the trap filter chamber because of the sudden pressure change between the pipe and trap filter chamber. It is desired that the particulate formation occur in the trap filter chamber. The particulates build up in the pipe and reduce its effective diameter. As the diameter of the pipe decreases, the pressure within the pipe increases which in turn causes an imbalance in the delicate pressure-vacuum in the LPCVD reactor and results in an unpredictable wafer deposition processing. Moreover, the particulates accumulating in the pipe may dislodge and migrate to the vacuum pump causing damage to the pump.
To alleviate the particulate build-up, costly maintenance cleaning schedule procedures have been implemented by semiconductor wafer manufacturers resulting in undesirable down-time.
Hence, a need exists for a chemical vapor deposition trap that reduces particulate by-product build-up at its inlet.